Distinct roles of the Na+ binding sites in the allosteric coupling mechanism of the glutamate transporter homolog, GltPh

1Citations
Citations of this article
7Readers
Mendeley users who have this article in their library.
Get full text

Abstract

Glutamate transporters carry out the concentrative uptake of glutamate by harnessing the ionic gradients present across cellular membranes. A central step in the transport mechanism is the coupled binding of Na+ and substrate. The sodium coupled Asp transporter, GltPh is an archaeal homolog of glutamate transporters that has been extensively used to probe the transport mechanism. Previous studies have shown that hairpin-2 (HP2) functions as the extracellular gate for the aspartate binding site and plays a key role in the coupled binding of sodium and aspartate to GltPh. The binding sites for three Na+ ions (Na1-3) have been identified in GltPh, but the specific roles of the individual Na+ sites in the binding process have not been elucidated. In this study, we developed assays to probe Na+ binding to the Na1 and Na3 sites and to monitor the conformational switch in the NMDGT motif. We used these assays along with a fluorescence assay to monitor HP2 movement and EPR spectroscopy to show that Na+ binding to the Na3 site is required for the NMDGT conformational switch while Na+ binding to the Na1 site is responsible for the partial opening of HP2. Complete opening of HP2 requires the conformational switch of the NMDGT motif and therefore Na+ binding to both the Na1 and the Na3 sites. Based on our studies, we also propose an alternate pathway for the coupled binding of Na+ and Asp.

Cite

CITATION STYLE

APA

Riederer, E. A., Moënne-Loccoz, P., & Valiyaveetil, F. I. (2022). Distinct roles of the Na+ binding sites in the allosteric coupling mechanism of the glutamate transporter homolog, GltPh. Proceedings of the National Academy of Sciences of the United States of America, 119(19). https://doi.org/10.1073/pnas.2121653119

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free